I (android kernel)
1.make sure this kernel configuration in MMC driver
CONFIG_MMC=y
# CONFIG_MMC_DEBUG is not set
CONFIG_MMC_UNSAFE_RESUME=y
# CONFIG_MMC_EMBEDDED_SDIO is not set
CONFIG_MMC_PARANOID_SD_INIT=y
#
# MMC/SD Card Drivers
#
CONFIG_MMC_BLOCK=y
CONFIG_MMC_BLOCK_BOUNCE=y
# CONFIG_MMC_BLOCK_PARANOID_RESUME is not set
# CONFIG_SDIO_UART is not set
# CONFIG_MMC_TEST is not set
#
# MMC/SD Host Controller Drivers
#
CONFIG_MMC_SDHCI=y
2.Disable this option
General setup --->
[ ] enable deprecated sysfs features to support old userspace tools
if choice it will open can't mount SD card error
3.filesystem support
File systems --->
DOS/FAT/NT Filesystems --->
<*> VFAT (Windows-95) fs support
-*- Native language support --->
<*> Codepage 437 (United States, Canada)
<*> Simplified Chinese charset (CP936, GB2312)
<*> NLS ISO 8859-1 (Latin 1; Western European Languages)
II (android system)
reference http://hi.baidu.com/jugege/blog/item/f58b2fdc13d770b5cc1166c7.html
1.start vold service
in init.rc start the vold service
service vold /system/bin/vold
socket vold stream 0660 root mount
ioprio be 2
2.configuration vold.fstab
/system/etc/vold.fstab
dev_mount sdcard /mnt/sdcard auto /devices/platform/s3c-sdhci.0/mmc_host/mmc0